Such a polishing arrangement is, for example, known from DE 27 42 113 A1. The polishing tool is adapted to reciprocate in a first direction. The workpiece in which the polishing tool dives is brought to rotate, so that a movement in a second direction between the polishing tool and the workpiece occurs. From the outside the workpiece is held by support wheels, which are at the same time driven to be rotating in order to rotate the tool.
Polishing, grinding and honing are methods of machining a surface to cause a material cutting with indefinite blades. Other machining methods, such as turning and milling, cause a cutting deformation of a surface with controlled cutting. Here, traces of the cutting are practically not avoidable.
While during grinding the surface machining practically exclusively results in a material cutting, polishing causes a plastic or partially plastic forming of roughness peaks on the surface structure, thus evening them out. The surface machining methods occurring in the micro or nano areas in the border area between micro-grinding and polishing have still not been completely explored in a scientific manner.
Also today, polishing of certain surfaces still takes place in a practically exclusively manual procedure. This is, for example, the case with tools to be used for the reshaping of metallic workpieces, for example by means of the cold flowing technique. Here, the structure of the polished tool surface has a crucial influence on the reshaping process and on the life duration of the reshaping tools. For the polishing, rotation-symmetrical reshaping tools are, for example, suspended in a rotary chuck of a polishing bench or a turning lathe and brought to rotate. An employee then polishes the function surfaces of the reshaping tool by means of a polishing tool that he reciprocates manually in parallel to the alignment. Polishing tools are typically polishing stones, for example made of silicium carbide (carborundum), or wooden sticks in connection with polishing means, for example diamond paste. During the polishing procedure, the employee frequently checks the result and varies different parameters, for example, the contact pressure, the rotation speed and/or his hand movement, and replaces the polishing tool on need, in order to make a stepwise approach to the desired polishing result. Each replacement of the polishing tool requires a careful cleaning of the surfaces to be polished to remove remains of the coarse polishing means before continuing the polishing with a finer polishing tool. Otherwise, remaining coarse polishing means can cause tracks on the workpiece surface during the subsequent polishing steps.
Thus, the polishing requires a substantial experience of the employee. Various parameters, which the employee can influence, will influence the polishing result, for example the way in which the employee performs his hand movement, when and how he replaces the polishing tool and how well he adapts the individual polishing steps to each other. In systems used for series production of products in large numbers, for example, cold moulders, in which uniform reshaping tools or reshaping tool parts are typically used in amounts of several hundreds of pieces per year, it is a disadvantage that the properties of such reshaping tools are dependent on the manual work of various employees. Thus, differences in the polishing quality cause too large deviations in the operating life of the reshaping tools. In this case the scatter range may scatter by a factor of 3 to 5.
The control of the polished surfaces is difficult. Thus, it will not be sufficient to evaluate the gloss of the surface. Reshaping tools with gleaming and thus apparently strong surfaces may fail quickly, if the surfaces have not been achieved through the correct polishing steps.
As it takes great effort to test the final quality of the surfaces, such tests are only made sporadically. The lack of process and product documentation counteracts the ensuring of a constant manufacturing quality and corresponds very poorly to the present documentation requirements, in particular in connection with certified manufacturing processes or systems.
Due to the large share of manual work, the manual polishing of reshaping tools is also very expensive. Further, the manual movements and the pressure to be performed cause a work load on the employee, particularly because typically these bodily working movements have to be performed for a whole workday at a time.
Additionally, the employee can only move the polishing tool at a limited speed and a limited contact pressure. In order to provide the polishing process with the mechanical output required for a good and fast polishing result, the rotation of the workpiece is usually chosen to be relatively fast. Consequently, the polishing path, that is, the path described by the polishing tool across the workpiece surface, runs substantially tangentially to the rotation of the workpiece, that is, substantially circularly. Typical machining tracks, such as rotation tracks, originating from former machining steps on the workpiece, typically also run tangentially and can therefore only difficultly be removed by means of manual polishing, which causes either long polishing durations or a poor end quality.
The relatively large hand movements of the employee—typically in the range of several centimeters—further cause that the axially central area of the workpiece is substantially more polished than the end areas. This is particularly the case with small workpieces. This axial irregularity of the polishing process also causes long polishing durations or poor polishing results in the area of the axial ends of the workpieces.
DE 199 47 006 A1 shows a grinding block holder that is used to perform the final grinding of a vehicle brake drum. The grinding block holder comprises a tool holder in which several grinding tools are inserted. The tool holder is fixed with bolts and springs to a holder in such a manner that it can move with several degrees of freedom. The force, with which the tool holder acts upon the workpiece, is set by means of a positioning.
US 2002/0031987 A1 shows a device, in which the surface of a disc is smoothed by honing. The tool used for the honing is suspended in a cardan-like manner, meaning that it can adjust its position in relation to the workpiece freely within certain limits.